Spark plug



May 1, 1928.

G. E. THEIS SPARK PLUG Filed April 1. 1925 Patented May 1, 1928.

UNITED, STATES PATENT OFFICE.

GEORGE EDWARD THEIS, OF ST. LOUIS, MISSOURI, ASSIGNOB, BY MESNE ASSIGN- MENTS, TO 0. JAECH, OF ST. LOUIS, MISSOURI.

SPARK PLUG.

Application filed April 1, 1925. Serial No. 19,949.

This invention relates to an improved spark plug and see is, among other objects, to provide a plug embodying a heating element for heating the fuel mixture in an engine cylinder so that the engine may be readily started.

Heretofore, electrical connection from the exterior of the plug has been made with an interior heating element in such a way as to require the use of cement to close the opening or passage accommodating the connection and it has been found that this cement, upon being directly subjected to the combustion occurring in an engine cylinder, becomes burned out with the result that the plug leaks compression. The present invention, therefore, further seeks to provide a plug wherein electrical connection with the heating element from the exterior of the plug will be accomplished in such a way that no cement will be used to effect the sealing of the plug, whereby the troubles incident to the use of cement will be avoided.

A further object of the invention is to provide a plug embodying a novel means for insulating the heating element and other electrically charged parts of the plug with respect to the plug shell.

And the invention seeks, as a still further object, to provide a plug embodying a novel means to compensate for the expansion and contraction of the plug shell whereby the plug is rendered permanently leak-proof.

Other and incidental objects will appear hereinafter.

In the accompanying drawings:

Figure 1 is a vertical sectional view through my improved plug.

Figure 2 is a horizontal sectional view on the line 2-2 of Figure 1, looking in the direction indicated by the arrows.

Figure 3 is a perspective view of the terminal collar and lead employed in connection with the heating element.

Figure 4 is a detail perspective View showing a slightly modified form of expansion fir carrying the invention into effect, I employ a shell threaded at its lower end for engagement in the spark plug opening of an engine cylinder and provided with an internal annular shoulder 11. Covering the inner surface of the shell is a coating 12 of re fractory insulating enamel fused on the shell. Resting on the shoulder 11 is a resilient compressible gasket 13 and overlying said gasket is a compensating ring 14 which may be of brass. The shoulder 11 of the shell is beveled and the lower face of the ring 14 is beveled in conformity with said shoulder. Overlying the compensating ring is a resilient compressible gasket 15 similar to the gasket 18 and, as shown, the inner peripheral margin of the upper face of said ring is beveled to substantially conform to the inclination of the beveled lower face of the ring while the outer peripheral margin of the upper face of the ring is flat. Extending through the gaskets 13 and 15 and the ring 14 is an insulator 16 which may be of porcelain. This insulator is provided with an annular enlargement or flange 17 having a beveled lower face to seat against the gasket 15 while below said flange the insulator is formed with a tapered lower extremity 18 extending to a point near the lower terminal of the shell. Integral with the shell at its upper end is a flange 19 which is formed over against the upper face of the flange 17 of the insulator for connecting the insulator with the shell and compressing the gasket 13 between the ring 1% and the shoulder 11 of the shell as well as compressing the gasket 15 between the flange 17 of the insulator and said ring. A sealed joint is thus provided between the insulator and the shell. Extending through the insulator axially thereof is a center electrode 20 equippedat its upper end with a clamping nut 21, and fixed to the shellat its lower terminal is a cooperating electrode 22.

Coiled around the lower tapered extremity 18 of the insulator 16 is a heating element 23 of suitable resistance wire. The coils of this element lie in spaced concentric relation to the insulator and the lower end of said element is fixed to the lower terminal of the shell while the upper end of said element is brazed or otherwise fixed to the expansion ring 14: at its inner circumference. Freely surrounding the upper end portion of the insulator 16 to rest on the flange 17 thereof is a collar 24 which forms an external electrical terminal for the heating element. Extending downwardly from said collar at one side thereof is a conductor 25 which is accommodated in a slot 26 in the flange 17 of the insulator and, at its lower end, is brazed or otherwise fixed to the ring 14: at its outer periphery. Thus, the collar is electrically Ill e sulator the plug,

.connected with the heating element 23 through the conductor 25 and expansion ring 14.

Attention is now directed to the fact that the refractory coating within the shell serves to protect the inner wall of the shell and will also tend to minimize expansion of the shell. Furthermore, this coating will serve, to insulate the coils of the heating element 23 with respect to the shell; so that vibration and consequent dislocation of the coils cannot-serve to'bring about short circuiting of the coils. It is, therefore, possible to space the coils from the lower extremity of the inso. that-the heat generated by the coils will not be directly communicated to the'in'sulator but, in the main, will be utilized'for heating the fuel charge. The coating-l2will also serve to insulate the ring let and conductor 25 with respect to the shell sothatwhen the plug is mounted upon an engine cylinderand the shell is thus electrically grounded, current may be supplied to theccollar 24 from the battery or other source or electrical energy upon the vehicle, for heating the coils of the heating element. Accordingly, when the fuel charge is drawn intov the cylinder, the charge will be heated by-said' element so; that the engine may be readily started. As will be observed, electrical connection with the heating element from the collar 24. is. effected without the use of cement to seal the plug sothat the troubles heretoforeexperienced by the use,

of' "cen1ent for this purpose, as previously pointed: out, are, therefore, avoided.

Expansion of; the plug shell, when the shell becomes heated incident to. the use of tends torelieve the pressure ofthe flange 1 9. of the shell on the flange 17 of the insulator with the result that the pressure on. the gaskets. 13 and 152'is correspond ingly relieved. "This, of course, tends to pro-' duce' leakage of the: plug and' various attemptshave 'heretofore been made to overcome leakage from this cause, the most coni-' mon expedient being to heat the flange 19- at the time it is formed over and coincident- 1y force the 'insulator downwardly into the shell for initially compressing the gaskets so that when flange cools, the gaskets will be subjected to a further extreme pres sure tending to compress the gaskets. In thus compressing the gaskets to an extreme point, the resiliency or expansible quality of the gaskets is relied upon to compensate for the expansion of the. plug shell. However, the expedient is more or less ineffectual and to overcome the defectI provide the compensating ring 1 1-. As will be seen. this ring will expand with the expansion of the shell so that pressure on the insulator is relieved' atthe flange 19 of the shell, a. cor responding-or even greater pressure on the gaskets 18 and 15 will "be, supplied by the expansion ofsaidring. The ring will, therefore, compensate for'the expansion, of the shell so that the pressure on the gaskets will be maintainedrelatively constant at all times and leakage of the plug thus etfectuallyprevented. i

In-Eigure 4 of the drawings, I have illustrated aslizght modification of the invention wherein the compensating ring,; indicated at 14:, is provided with an exterior coating 27 of enamel, fused on the ring.- This coating will, therefore, serve to insulate the ring with respect to. the plug shell so that. coating of the shell with enamel will be rendered unnecessary. i i

Having thus described the invention, what I claimis: i i

In a spark plug, a shell having an. inner beveled shoulderQan insulator within the shell having an annular enlargement beveled upon its. lower face toinatch-the beveled shoulder of the shell, a temperaturecomg-f pensating ring mounted upon the insulator between; the enlargement thereof and the shoulder of the shell, and having the outer portion of its lower face and theinner portion of its upperface-similarly bevel-ed to match the beveled faces of the shoulder and enlargement, and hfaving the inner portion: of its lower face and the outer portion of its upper face flat and-parallel, and com-7' pressible gaskets at opposite sides of thesaid ring and confined. between it and the said shoulder and enlargement.

In testimony whereof I aifix my signature.

GEQRG'E TH EIS. [as] 

